The results of follow-up observations of the TeV \gamma -ray source HESS J1640 - 465 from 2004 to 2011 with the High Energy Stereoscopic System ( H.E.S.S . )
are reported in this work .
The spectrum is well described by an exponential cut-off power law with photon index \Gamma = 2.11 \pm 0.09 _ { \mathrm { stat } } \pm 0.10 _ { \mathrm { sys } } , and a cut-off energy of E _ { c } = 6.0 ^ { +2.0 } _ { -1.2 } TeV .
The TeV emission is significantly extended and overlaps with the north-western part of the shell of the SNR G338.3 - 0.0 .
The new H.E.S.S .
results , a re-analysis of archival XMM-Newton data , and multi-wavelength observations suggest that a significant part of the \gamma -ray emission from HESS J1640 - 465 originates in the SNR shell .
In a hadronic scenario , as suggested by the smooth connection of the GeV and TeV spectra , the product of total proton energy and mean target density could be as high as W _ { p } n _ { H } \sim 4 \times 10 ^ { 52 } ( d / 10 \mathrm { kpc } ) ^ { 2 } erg cm ^ { -3 } .